FIG. 1 is a conceptual view of general color matching.
Input data as RGB data is converted into XYZ data on a device-independent color space by an input profile. Since colors outside the color gamut of an output device cannot be expressed by the output device, the input data converted into data on the device-independent color space undergoes gamut mapping, so that all such colors fall within the color reproduction range of the output device. After gamut mapping, the input data is converted from the data on the device-independent color space into CMYK data on a color space depending on the output device.
In color matching, a reference white point and ambient light are fixed. For example, in profiles specified by International Color Consortium (ICC), the Profile Connection Space (PCS) that connects profiles are defined by XYZ values and Lab values of the D50 reference. For this reason, upon viewing an input document or printout under a light source with the D50 characteristics, correct color reproduction is guaranteed. Under light sources with other characteristics, correct color reproduction is not guaranteed.
In consideration of this, the present applicant has proposed color matching according to the viewing conditions (Japanese Patent Laid-Open No. 2000-50086). This proposal is color matching that uses forward color appearance conversion according to the viewing conditions on the source side, and inverse color appearance conversion according to the viewing conditions on the destination side.
However, since the technique disclosed in Japanese Patent Laid-Open No. 2000-50086 (U.S. Pat. No. 6,542,634) performs processing without distinguishing a device which handles object colors and that which handles light-source colors, there is room for improvement so as to implement color matching with higher precision.